Chronology: This verse is the essential baseline for calculating dates in the Book of Mormon. Internally, the Book of Mormon is consistent in its dating, strictly accounting for the years down to the time of Christ. The chronological problem is not internal, but external. When the six hundred years are applied to real-world history, the sum is less than six hundred.
The two points which fix the Nephite calendar to a known date are the first year of the reign of Zedekiah (in 597 B.C.) and the plausible birth of Christ. Of these two dates, only the fall of Jerusalem is confirmed in world history. The date of Jesus’s birth is calculated by various means. Popular belief assumes that our current count is accurate, while scholarly consensus places Jesus’s birth a few years earlier. As Randall Spackman points out:
The Gospel of Matthew records that “Jesus was born in Bethlehem of Judea in the days of Herod the king” (Matt. 2:1). Josephus reports that at the Passover feast following Herod’s death, a riot broke out and many were killed. Varus, the Roman governor of Syria, marched his forces to Jerusalem and left one of his legions there to maintain order. Because coins bearing Varus’ name indicate he was governor of Syria from 6 B.C. through 4 B.C., the death of Herod very likely occurred before Passover in the year 4 B.C.—and hence the birth of Christ earlier than that.
Thus, instead of a span between 600 B.C. and 1 B.C. (599 years), the time between Lehi’s departure and Christ’s birth was from 587 B.C. to 4 B.C. (583 years). Nevertheless, the Nephite reckoning counts six hundred years. How might the Nephite count be reconciled with external history?
The modern reader simply assumes that a “year” is three hundred and sixty five days. This “year” is based on a solar calendar. Israel had used a lunar calendar in Lehi’s day. A lunar calendar assigns an average of 354.367 days per year, which is eleven days fewer than a solar calendar (365.2422 days per year). The later Qumran community (beginning some time before 134 B.C.) advocated a 364-day solar calendar rather than the 354-day lunar calendar that was still in use by the Jerusalem religious leaders.
There are 600 lunar years between the departure of Lehi’s family and the probable birth of Jesus. Consequently, I use lunar-year calculations in this commentary, yielding dates different from those listed at the foot of the pages in the Book of Mormon, but which provide a closer correlation between Book of Mormon events and secular history. Dates noted in this commentary have been recalculated according to a lunar year correlation.